Open the Phone app
Tap Recents, Contacts, or Favorites
Select the contact you want to block
Tap the More options menu
Tap Block number or Block contact
Confirm the block
Open the Contacts app
Select the contact
Tap the More options menu
Tap Block contact
Confirm the block
Open the Messages app
Open the conversation
Tap the More options menu
Tap Details
Tap Block and report spam or Block
Confirm the block
Open the Phone app
Tap Settings
Tap Blocked numbers
Add the number you want to block
To unblock a contact
Open the Phone app
Tap Settings
Tap Blocked numbers
Remove the contact or number from the blocked list